Amphiphilic Graphene Oxide Research Articles

Dispersion of polyacrylamide and graphene oxide nano-sheets for enhanced oil recovery

Hydrolysed polyacrylamide (HPAM) is widely used in enhancing oil production during tertiary flooding processes by improving the sweep efficiency . However, HPAM faces many challenges under high-temperature and high-salinity conditions mainly caused by the degradation. To overcome these challenges, incorporation of approprioate nanoparticles into HPAM solutions have been recently suggested to enhance its performance during the enhanced oil recovery (EOR) process. The current study specifically investigated the potential of amphiphilic graphene oxide (GO) in enhanicng the performance of HPMA. Its influences on HPAM in terms of the surface activity at the oil-water interface, the mobility behaviour, and the effectiveness in oil recovery were examined. The results revealed that adding up to 0.8 wt% of GO into HPAM reduced the oil-water interfacial tension (IFT) from 62.54 mN/m to 42.78 mN/m, and the contact angle (CA) from 71.08º to 68.84º, while in the mean time increasing the viscosity from 9.07 mPas to 16.49 mPas. Furthermore, the pilot core-flooding study demonstrated that with an addition of 0.8 wt% GO, HPAM achieved higher oil recovery rate (i.e., 76.83 %) than that of the pure HPAM (i.e., 67.39 %). The improved oil recovery performance was attributed to a better mobility ratio, resulting from the increased viscosity of the composite and reduced IFT, which was facilitated by the amphiphilic behaviour of GO, as supported by the desirability model.

Fluffy-like amphiphilic graphene oxide and its effects on improving the antibacterial activity and thermal outstanding of ethyl cellulose /polyvinyl alcohol hydrogel film

The antibacterial characteristics of graphene oxide (GO-SB) nano-sheets generated by charring sugarcane bagasse (SB) are described in this study. The antibacterial capability of GO-SB was improved when it was grafted with ethyl cellulose (EC) and polyvinyl alcohol (PVA) to form GO-SB/EC/PVA hydrogels. Characterization of GO-SB nanosheets and GO-SB/EC/PVA hydrogels was accomplished by using FTIR, SEM, XRD, and thermal studies. The antimicrobial activity was carried out against Gram positive bacteria [Micrococcus leutus & Staphylococcus aureus], Gram negative bacteria [Escherichia coli, Pseudomonas aeruginosa] and pathogenic fungal yeast [Candida albicans] applying the disc diffusion method. The disc diffusion method results showed that the improved GO-SB/EC/PVA exhibited a reasonable level of antimicrobial capability against Micrococcus leutus, demonstrating that the antimicrobial improvement of GO-SB was more effective in the GO-SB/EC/PVA hydrogels by increasing the inhibition zone of Gram-positive bacteria, Micrococcus leutus from (13.0 to 16.0 mm).Graphical abstract

In-situ constructing hybrid cross-linked networks in brominated butyl rubber via amphiphilic graphene oxide cross-linkers: Retaining excellent gas barrier and mechanical properties after fatigue

Rubber/graphene nanocomposites as gas barrier materials have attracted great interest in recent years. However, it is still a challenge to construct strong covalent interfaces between nonpolar rubber matrix and graphene for retaining excellent gas barrier and mechanical properties of aircraft tires after fatigue. In this work, hybrid cross-linked networks in brominated butyl rubber (BIIR) are first proposed and in-situ constructed successfully via introducing the amphiphilic graphene oxide cross-linkers (R-aGO). R-aGO can participate in the curing of BIIR to form hybrid cross-linked networks, which can force R-aGO to move with BIIR synchronously during fatigue deformation due to strong interfaces between BIIR and R-aGO via covalent bonds. When R-aGO content is 3 phr, the BIIR/R-aGO nanocomposites show a 27 % improvement in gas barrier property, a 230 % increase in strength at 40 % strain (suffered deformation of aircraft tires), and a 229 % enhancement in tensile strength relative to conventional BIIR/aGO nanocomposites with interfacial modifiers. More importantly, BIIR/R-aGO nanocomposites still retain excellent gas barrier and mechanical properties even after 500,000 load cycles (40 % strain). This work provides a novel route to fabricate rubber/graphene nanocomposites with superior gas barrier and mechanical properties, especially after fatigue.

The foam reinforced with Janus amphiphilic graphene oxide to control steam channeling in heavy oil reservoir

Foams have been considered effective diverters to decrease the mobility in the steam channel for heavy oil-recovery processes. Due to the high weight of chemical additive loss caused by adsorption to the rock surface and the poor thermal stability of these additives, the result of surfactant or polymer is usually unsatisfactory. To avoid these problems, nanoparticles can be utilized as novel assistants to enhance the generation and stabilization of foams. In this research, an amphiphilic graphene oxide (H-GO2), which is very effective at low concentrations, is utilized to enhance the foam performance in the process of plugging steam channeling. Compared with the foam prepared by using surfactant alone, the foam height and half-life at a low concentration (0.05 wt%) of H-GO2 in bulk medium increased by approximately 151% and 341%, respectively. The size distribution of bubbles in the presence of 0.05 wt% H-GO2 is uniform, and H-GO2 creates the gas-liquid interface film three times thicker than that of the surfactant without H-GO2. As NaCl concentration increased from 0.5 to 5 wt%, more foam was generated in a shorter time, and the half-life became longer. Excess NaCl causes less foam formation and a shorter half-life. Foam generation and stabilization are reduced with the CaCl2 concentration in solution increasing from 0 to 10 wt%, or the temperature increasing from 150 to 240 ℃. Corefloods with coinjected CO2 and water containing 0.05 wt% H-GO2 and surfactant can double the resistance factor of foam in the porous medium, compared with coinjection of CO2 and water containing only surfactant. The additional oil recovery of foam generated by surfactant alone is 14.6%. It is extraordinary that the increased recovery of 31.4% can be obtained by introducing only 0.05 wt% H-GO2 into the same foam. This work may provide a reference for steam channeling control in the steam injection development process of heavy oil oilfields.

Dispersibility study of GO-like biocarbons obtained from the thermal decomposition of biomass: Phragmites australis and Carya illinoinensis

In this work, we develop a cost-effective and straightforward methodology to upgrade earth-abundant biomass into high-value-added graphene oxide-like dispersions. The main idea is based on a controlled thermal treatment allowing the conversion of the two different biomass sources with different lignin content (Phragmites australis and Carya illinoinensis), in an air atmosphere and in a short time (15 min); no additional functionalization, catalysts, or high temperatures are necessary. The interface of both biocarbons is distinguished by different proportions of hybridized carbons (CC and C–C) and functional oxygenated groups (OH, C–O, CO, C–OH), characteristic of amphiphilic graphene oxide and responsible of the interactions with solvents. The results show that the most stable dispersions were achieved using polar solvents (Zave < 300 nm, ζ ±15 mV) with no surfactants. Also, we determined the dispersion states (qualitatively and quantitatively) and their zeta potential for all dispersions as well as a graphical map of their behavior, indicating that polar solvents promote the formation of stable dispersions, whereas non-polar solvents sediment instantly. The strategy reported here may be a feasible and unique approach to formulate stables dispersions using graphene based-materials obtained in a sustainable way, which have the potential for future applications in ink formulation for inkjet printing and electrochemical applications.

Hydrodeoxygenation of Bio-Oil over an Enhanced Interfacial Catalysis of Microemulsions Stabilized by Amphiphilic Solid Particles

Bio-oil emulsions were stabilized using coconut shell coke, modified amphiphilic graphene oxide, and hydrophobic nano-fumed silica as solid emulsifiers. The effects of different particles on the stability of bio-oil emulsions were discussed. Over 21 days, the average droplet size of raw bio-oil increased by 64.78%, while that of bio-oil Pickering emulsion stabilized by three particles only changed within 20%. The bio-oil Pickering emulsion stabilized by Ni/SiO2 was then used for catalytic hydrodeoxygenation. It was found that the bio-oil undergoes polymerization during catalytic hydrogenation. For raw bio-oil hydrodeoxygenation, the polymerization reaction was little affected by the temperature below 200 °C, but when the temperature raised to 250 °C, it was greatly accelerated. However, the polymerization of monocyclic aromatic compounds in the reaction process was partially inhibited under the bio-oil Pickering emulsion system. Additionally, a GC-MS analysis was performed on raw bio-oil and hydrodeoxygenated bio-oil to compare the change in GC-MS-detectable components after hydrodeoxygenation at 200 °C. The results showed that the Pickering emulsion catalytic system greatly promoted the hydrodeoxygenation of phenolic compounds in bio-oil, with most monocyclic phenolic compounds detected by GC-MS converting to near 100%.

Amphiphilic graphene oxide membranes for oil–water separation

Amphiphilic graphene oxide membranes for oil–water separation

Experimental study of an amphiphilic graphene oxide based nanofluid for chemical enhanced oil recovery of heavy oil

Amphiphilic GOC nanosheets in situ form a viscoelastic emulsion, which achieves mobility control ability to enhance oil recovery.

Experimental and molecular dynamic studies of amphiphilic graphene oxide for promising nanofluid flooding

Owing to its extremely high aspect ratio, water dispersibility, and dramatic lightness, graphene oxide (GO) has been considered a promising alternative to chemical enhanced oil recovery (CEOR). However, the long-term stability of GO under reservoir conditions and the mechanisms underpinning the cost-effectiveness of this nanofluid flooding remain underexplored. Herein, a two-dimensional (2D) GO derivative in the form of amphiphilic graphene oxide (GOA) composed of a hydrophobic graphene center and a hydrophilic polyethylene glycol periphery for CEOR was investigated by combining experimental characterizations and molecular dynamics simulations. The thickness of the GOA is only 2.33 nm, but the lateral dimension extends up to a few micrometers, which endows GOA with good dispersibility and stability in brine. GOA functions as a 2D amphiphile, which adheres to the interface and decreases the interfacial energy after reaching a threshold concentration as low as 45 mg/L. These nanosheets spontaneously accumulate at the oil–brine interface to produce colloidal lamellae with higher local viscosity at the water–oil interface. GOA tuned the oil-wet and water-wet surfaces to almost neutrally wet surfaces, but the amount of physical adsorption of GOA was rather low. GOA-based nanofluid has desirable compatibility with rock pores. The oil recovery factor of GOA-based nanofluid after extensive brine flooding was characterized at the pore scale, being 18.2 % of the original oil in place at a GOA concentration of 100 mg/L. The dimensionless capillary number of GOA-based nanofluid flooding is ∼ 1000-fold that of brine flooding. The results confirm that this atomically thin, amphiphilic, highly water dispersible 2D sheet should enable highly cost-effective application in CEOR.

Electro‐Thermo Controlled Water Valve Based on 2D Graphene–Cellulose Hydrogels

AbstractNovel 2D hydrogels with coupled electro‐thermoregulation for water transport are constructed via self‐assembly of hydroxypropyl cellulose (HPC) with graphene oxide (GO) and reduced GO (rGO), where the capability of HPC to switch between hydrophobic and hydrophilic states is exploited. Amphiphilic GO surface is used to guide the ordering and alignment of liquid crystalline HPC domains. The changes in conformation and alignment of HPC serve as a switch for optical properties and water transport. A composite consisting of electrically conductive rGO and 2D hydrogel is developed to produce thermal stimulus and thus construct an electro‐thermo controlled valve for regulated water transfer. The prepared 2D hydrogel has a large swelling rate, outstanding mechanical properties (Young's modulus is 2.5 GPa), and superior electrical conductivity (176 S cm−1). The ability of HPC domains to change conformation in 2D confinement, when Joule heating is applied, can function as a 2D low footprint water switcher with optical control in smart membranes. The proposed sustainable approach to self‐assembly of HPC in 2D confinement of GO and rGO is applicable to the whole family of lower critical solution temperature polymers. Thus, a ubiquitous and sustainable synthesis of novel low dimensional robust multifunctional hydrogels is demonstrated.

Fabrication of novel PNIPAM@GO microspheres loaded with dual drugs featuring on‐demand drug release capability

AbstractIn this research, we successfully prepared a new kind of core‐shell microspheres (PNIPAM@GO) composed of hydrophilic poly (N‐isopropyl acrylamide) (PNIPAM) nanoparticles as the core and amphiphilic graphene oxide (GO) nanosheets as the shell through hydrogen bonding and self‐assembly in organic solvent. The temperature‐sensitive behavior of the PNIPAM core made its average size decrease from 888.3 nm to 630.3 nm with temperature increasing from 25°C to 50°C. And the GO shell could give PNIPAM@GO microspheres remarkable photothermal effects in water under NIR laser irradiation (808 nm) for 20 min. Further, doxorubicin (DOX) and 5‐fluorouracil (5‐FU) were loaded into the core and the shell with loading efficiency of 81% and 11%, respectively. By turning on/off NIR irradiation, the PNIPAM@GO microspheres could respond to the heat generated from GO shell by volume shrinkage, thus on‐demand controlling the drug release. The in vitro biological assessment verified that the samples prepared here were biocompatible. The developed platform shows a potential application in chemo‐photothermal therapy of cancers in the future.

Demulsification of Heavy Oil-in-Water Emulsion by a Novel Janus Graphene Oxide Nanosheet: Experiments and Molecular Dynamic Simulations

Various nanoparticles have been applied as chemical demulsifiers to separate the crude-oil-in-water emulsion in the petroleum industry, including graphene oxide (GO). In this study, the Janus amphiphilic graphene oxide (JGO) was prepared by asymmetrical chemical modification on one side of the GO surface with n-octylamine. The JGO structure was verified by Fourier-transform infrared spectra (FTIR), transmission electron microscopy (TEM), and contact angle measurements. Compared with GO, JGO showed a superior ability to break the heavy oil-in-water emulsion with a demulsification efficiency reaching up to 98.25% at the optimal concentration (40 mg/L). The effects of pH and temperature on the JGO’s demulsification efficiency were also investigated. Based on the results of interfacial dilatational rheology measurement and molecular dynamic simulation, it was speculated that the intensive interaction between JGO and asphaltenes should be responsible for the excellent demulsification performance of JGO. This work not only provided a potential high-performance demulsifier for the separation of crude-oil-in-water emulsion, but also proposed novel insights to the mechanism of GO-based demulsifiers.

Fluffy-like amphiphilic graphene oxide (f-GO) and its effects on improving the antifouling of PAN-based composite membranes

Membrane fouling remains a significant restriction for the long-time operation. In this paper, fluffy-like amphiphilic graphene oxide (f-GO) was prepared by simple grafting silane coupling agent (KH-570) onto the graphene oxide matrix, and thus featured with good dispersion behavior in organic solution. The f-GO was further incorporated into the PAN-based (poly(acrylonitrile-methyl acrylate), P(AN-MA)) copolymer during the phase inversion process. Compared with the P(AN-MA) membrane, the resistance of the f-GO/P(AN-MA) composite membrane reduced from 4.49 × 10−12 m−1 to 1.78 × 10−12 m−1. The pure water flux increased from 200 to 326 L/m2h, while the water contact angle declined from 92.8° to 68.3°. It is worthy to note that the fouling mode changed from irreversible fouling to reversible fouling, with the total fouling rate showing a half decay. The fouling recovery rate reached 98.16% and the BSA rejection rate increased from 70.59% to 99.33% as 0.5 wt% f-GO was incorporated. The f-GO is easily scaled up and can be widely applied in other polymer matrices, showing potential application prospects in the membrane separation and purification area. The f-GO/P(AN-MA) composite membranes with excellent water flux, BSA rejection and FRR, are candidates for further employment in wastewater purification applications.

Construction of Polymer Brushes-Decorated Amphiphilic Janus Graphene Oxide Nanosheets Via Pickering Emulsion Template for Catalytic Applications

Construction of Polymer Brushes-Decorated Amphiphilic Janus Graphene Oxide Nanosheets Via Pickering Emulsion Template for Catalytic Applications

Reinforcing natural rubber by amphiphilic graphene oxide for high-performance catheters

Graphene oxide (GO) has been considered as a promising nanofiller to reinforce water-borne polymer due to its exceptional mechanical properties and good dispersibility in an aqueous solution. However, the re-aggregation of hydrophilic GO sheets in a hydrophobic polymer matrix with the evaporation of water, resulting from remarkable discrepancy of the interfacial energy, remains a significant challenge to achieve the high-performance GO-based polymer nanocomposites. Herein, the amphiphilic graphene oxide (AGO) rather than the conventional GO is applied to enhance the mechanical properties of natural rubber latex (NRL) through simple solution blending. Our results show that the AGO demonstrates not only good dispersibility in the NRL aqueous solution but also strong hydrophobic interaction with the NRL particles. Benefiting from this amphiphilic character, the good dispersibility of AGO in the NRL matrix is realized after the oven-drying process, leading to a simultaneous enhancement in tensile strength (up to 35 MPa) and elongation at break (up to 1100%). In particular, it is found that the NRL tube, a kind of catheter, demonstrates a remarkable improvement in both blasting pressure, blasting volume with just a small amount addition of AGO (as less as 0.1%). This work provides a simple, green, and efficient route to fabricate high-performance polymer latex/graphene nanocomposites.

Fabrication of Amphiphilic Graphene Oxide—Polyoxometalate with Temperature Response for Epoxidation of Olefin in Water

Here, amphiphilic graphene oxide–polyoxometalate (GO-POM) was fabricated using a new strategy involving control of the stacking of GO lamellae through phosphoric acid and exfoliation by H2O2. The additions of H3PO4 and H2O2 were essential for the formation of the catalytic center of peroxo-POMs. The GO-POM hybrid had one side with hydrophilic properties and another side with hydrophobic properties, which conferred temperature-responding properties. GO-POM could catalyze the epoxidation of cyclooctene with complete conversion and 98% selectivity for epoxide at 50 °C for 12 h in water. Meanwhile, the catalyst could be easily recycled because of its thermosensitive property.

Triple Phase Inversion of Emulsions Stabilized by Amphiphilic Graphene Oxide and Cationic Surfactants.

Amphiphilic graphene oxide (A-GO) with grafted octylamine was prepared via a one-step method of N,N′-dicyclohexylcarbodiimide coupling and epoxide ring opening at a mild temperature of 40 °C. The phase of oil–water emulsion stabilized by the complexes of A-GO and the cetyltrimethyl ammonium bromide (CTAB) surfactant could invert three times by adding CTAB or A-GO. This process was called triple phase inversion, which was a function of the concentration of A-GO or CTAB surfactants. The conductivity and zeta potential measurements confirmed that CTAB could influence the carboxyl ionization of A-GO. In addition, the turbidity of the A-GO and CTAB mixed dispersion system revealed that the appearance and disappearance of precipitation occurred when CTAB or A-GO concentration was increased. Meanwhile, the emulsion prepared by mixing the dispersion with an equal volume of xylene at a fixed CTAB concentration also showed triple phase inversion as the A-GO concentration varied. Results indicated that the stability of the emulsion and the size of the emulsion droplets had a certain correlation during the phase inversion process, which varied with the concentration of CTAB or A-GO.

Study of Janus Amphiphilic Graphene Oxide as a High-Performance Shale Inhibitor and Its Inhibition Mechanism.

Janus amphiphilic graphene oxide (JAGO), modified by dodecylamine on one side of graphene oxide (GO), was investigated for its novel use as a shale inhibitor. JAGO was synthesized by the Pickering emulsion template technology and was characterized by the Fourier-transform infrared spectra, UV-vis spectra, and transmission electron microscopy. Compared to KCl (5%), polyether diamine (2%), and pristine GO (0.2%), JAGO's highest shale recovery rate (75.2% at 80°C) and lowest swelling height of Mt-pellets (2.55 mm, 0.2%) demonstrated its excellent inhibitive property. Furthermore, JAGO acted as a perfect plugging agent and greatly reduced filtration loss. Based on the results of X-ray diffraction, contact angle measurements, and pressure transmission tests, we proposed that the 2D nano-sheet amphiphilic structure of JAGO, which enabled it to be effective both in chemical inhibition and physical plugging, was responsible for its remarkable inhibition performances.

Preparation and aggregate state regulation of co-assembly graphene oxide-porphyrin composite Langmuir films via surface-modified graphene oxide sheets

Constructing graphene oxide (GO)-based 2D nanomaterials via facile and appropriate methods have aroused much attention due to their potential applications in many fields. Herein, by Langmuir-Blodgett (LB) technique, we have successfully fabricated GO-based films composited with porphyrin molecules. By the reaction of diazotization and Fischer osazone, different surface states of GO sheets with sulfonate groups were obtained. The amphiphilic GO and surface modified GO sheets could spontaneously form composite films at the air/water interface with porphyrin molecules (TMPyP) by electrostatic interactions and π-π stacking. Since the sheets can perfectly float on the interface, the TMPyP molecules were adsorbed on the floating-layers and self-assembled into highly ordered J-aggregate structures. The morphological characterization results showed the composite films with smooth and dense surface. Due to the different surface state of the nanosheets, the aggregate states of porphyrin molecules were different which could be demonstrated in the UV–vis spectra. The results indicated that the induction of sulfonate groups and the types of oxygen-containing groups have played important roles for regulating the aggregate state of porphyrin molecules.

Electrically conductive and elastoplastic carbon nanohybrid preform reinforced by physical cross-linking

ABSTRACTEfficient buildup of carbon nanomaterial network with isotropic structure and performances in viscous polymer bulk has been of intense interest for abundant range of applications. Herein, a conductive and elastoplastic carbon nanohybrid preform is prepared. The strategy for assembling structurally intact carbon nanotubes (CNTs) and amphiphilic graphene oxide (GO) into integral carbon nanohybrid framework is implemented by using 2-ethyl-4-methylimidazole (EMI) during an undisturbed reaction. The as-synthesized porous carbon nanohybrid preform with sandwich cell wall was characterized with respect to wettability, electrical conductivity, and structural robustness to evaluate the structural and functional synergies from GO sheets and CNTs. Significantly increased conductivity is ascribed to the networking sp2-hybridized carbon domains interconnected by CNT bridges. The hydrogen-bonded EMI chains functioning as physical cross-linking are responsible for the elastoplasticity of carbon nanohybrid preform. A mechanism underlying is proposed for the conversion from common carbon nanomaterials to three-dimension multifunctional reinforcement.